Auxiliary flow valve system and method for managing load flow requirements for auxiliary functions on a tractor hydraulic system

ABSTRACT

A system and method for managing hydraulic fluid load flow requirements for a tractor having a single pump hydraulic system. The system and method controls an implement hydraulic system and an auxiliary implement hydraulic system using a single hydraulic pump. The auxiliary flow valve system and method of the present disclosure gives precedence to the auxiliary functions so as to maintain full function of the auxiliary device. It also may supply a reduced flow, less than the maximum available from the system hydraulic pump to the auxiliary device. The remaining flow is available to the implement hydraulic system, with full flow being available to the implement when no auxiliary function is used. It also provides the ability to use a closed center valve in a load sensing system by bleeding flow pressure from the auxiliary hydraulic system.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. Provisional Patent Application No. 61/564,690 filed Nov. 29, 2011, herein incorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to land vehicle hydraulic systems generally and more specifically to pipelayer hydraulic assemblies mounted to track-type tractors.

BACKGROUND OF THE INVENTION

Hydraulic track-type pipelayers consist of a track-type crawler tractor with a pipelayer draw works structure mounted to it, along with the associated hydraulic hook and boom winches, the winch hydraulic-controls, and all the necessary rigging (per ISO 8813=mechanism to position the boom and hook). The track-type crawler tractor provides the power to drive the hydraulic winches, and any other hydraulic system fitted or used to control the crawler tractor.

The pipelayer (implement) hydraulic system can be driven either directly with a dedicated implement pump supplying only the pipelayer system, or connected in parallel with the tractor hydraulic implement system. The tractor implement system is also arranged in parallel. A parallel system means that when hydraulic functions are actuated simultaneously, hydraulic fluid flow is divided to each function. It is known however, that there will be a greater flow to the path with the least resistance. Due to this fact, when the pipelayer implement is connected to the tractor implement system in parallel, either the tractor implement system or the pipelayer system could be impaired when used simultaneously. This is because the fluid directed to the path of least resistance could leave the other system with insufficient hydraulic pressure to adequately operate that system. This is typically not an issue with the pipelayer system, since all other existing implements—bulldozer cylinders, rippers, tow winches, etc.—are typically either removed or disconnected, or are not used during critical pipelaying operations. The same is not true, however, for essential hydraulic operations such as the tractor steering system and certain other auxiliary hydraulic systems.

Crawler tractors have two methods for steering control: mechanical steering clutches, or hydraulic differential steering. Mechanical steering clutches are completely separate from the hydraulic implement system, and are unaffected by it. Hydraulic differential steering systems use a hydraulic steering motor to facilitate a change of direction. The hydraulic steering motor can be powered either by its own dedicated pump, separate from the implement system (a two-pump system), or by the tractor implement pump (a single-pump system).

In a single pump system, the steering function could be severely compromised unless it is given precedence over the other tractor implement functions. With a pipelayer connected directly to a single-pump system which also services the steering function, the steering of the tractor could be drastically impaired if a load placed by the pipelayer implement consumes hydraulic flow, leaving insufficient flow for the steering function. For example, if the tractor was making a turn while quickly raising an empty hook, the hook winch would have a very low pressure requirement (least resistance) while having a high flow requirement. In this example, the majority of hydraulic fluid would flow through the pipelayer's hook circuit, leaving significantly less, and potentially insufficient, flow for the steering function. This is an extremely undesirable situation. For this type of reason, single pump differential steering systems have not been successfully implemented on tractors including implements such as pipelayers, and therefore pipelayers have been primarily used on crawler tractors with mechanical steering clutches. A need, therefore, exists for a single pump differential steering system and method for a tractor including hydraulic implement, such as a pipelayer connected in parallel thereto, wherein the tractor steering system, or any other essential hydraulic system, is not affected by the hydraulic flow requirements of the implement (pipelayer).

Auxiliary implements may also be connected to the tractor hydraulic system in addition to the implement hydraulic system. Auxiliary implements may include a pipelayer counterweight used to counter (or balance) the weight forces exerted on one side of the tractor by the weight of the draw works structure (plus the weight of the pipe or other apparatus which may be supported therefrom). Traditionally, pipelayer tractor hydraulic systems have used a small dedicated pump, most commonly of a fixed displacement type, to supply the hydraulic flow requirements of the auxiliary implement which is separate from the main draw works implement pump (or pumps in dedicated pump, or two-pump draw works systems). A need also exists for a load flow management system for a tractor having a hydraulic implement and a hydraulic auxiliary implement in a single pump hydraulic system so as to not affect the hydraulic flow requirements of the auxiliary implement by the hydraulic flow requirements of the implement.

SUMMARY OF THE INVENTION

The auxiliary flow valve system and method of the present disclosure controls an implement hydraulic system such as a pipelayer draw works structure with an auxiliary implement, such as a counterweight, or multiple auxiliary implements using a single hydraulic pump. The present auxiliary load flow valve system and process gives precedence to the auxiliary system (counterweight) which is in hydraulic fluid communication with an implement system (pipelayer), by allowing the hydraulic power (pressure and flow) to be controlled in the auxiliary hydraulic system independently of the hydraulic pressure requirements of the implement hydraulic system. As a result, full control of the auxiliary hydraulic operation is maintained regardless of the implement system demands. A secondary function and sub-process also allows either the auxiliary system, or the implement system, to dictate the pump's supply-pressure output. As used herein, the term auxiliary system or auxiliary implement shall include any hydraulic system which relates to an additional or support implement operation and function, such as, but not limited to, a hydraulic flow tractor counterweight. Also as used herein, the term implement system shall mean any tractor primary implement operation and function such as, but not limited to, a hydraulic pipelayer draw works.

In its general form, the present disclosure includes a process for managing fluid flow for a tractor implement and an auxiliary implement connected in parallel to a single hydraulic pump. The process includes the steps of determining the implement fluid pressure requirement; determining the auxiliary implement fluid pressure requirement; and maintaining the auxiliary implement fluid pressure requirement by providing fluid flow to the auxiliary implement regardless of the implement fluid pressure requirement.

The hydraulic auxiliary flow valve of the present disclosure allows the use of a single pump to supply both the implement (pipelayer draw works) and auxiliary implements (tractor counterweight and other auxiliary implements). It can be used with a variable displacement load sensing pump, or a fixed-displacement pump.

The auxiliary flow valve system and method of the present disclosure may utilize the same or similar main-logic element as described in our U.S. Utility patent application Ser. No. 12/843,835, incorporated fully herein by reference. The auxiliary flow valve of the present disclosure, in contrast, gives precedence to the auxiliary functions and supplies a reduced flow, less than the maximum available from the main draw works implement pump, to them; the remaining flow being available to the draw works, with full flow being available to the draw works when no auxiliary function is used. The auxiliary load flow valve system and method of the present disclosure also provides the ability to use a closed center valve—typically used with pipelayer counterweight controls—in a load sensing system. The load flow valve system described in our U.S. application Ser. No. 12/843,835 gives precedence to the tractor's essential operations, such as the steering, and does not describe the ability to use a closed center valve, however, this functionality could be added externally to the circuit. Another main difference with the valve system of the present disclosure is that the amount of flow going to the auxiliary hydraulic system is limited since it will never require full pump flow, but still give it priority since it is more crucial to operate when demanded the previous load-flow valve of the previous disclosure gave complete priority to the steering system, right up to complete pump flow if required. The valve system of the present disclosure, the implement system will always be able to operate even when the auxiliary system is at full speed operation.

One of the main benefits of the auxiliary flow valve system and the method of the present disclosure is that it eliminates the need for additional pump drives which are increasingly difficult to accommodate in confined tractor engine compartments. In addition, since it may be mounted remotely from the engine drive, it provides more flexibility for installation in tight confines over traditional dedicated auxiliary hydraulic pump systems.

In a preferred embodiment, the present disclosure includes a process for managing hydraulic fluid flow requirements for an implement hydraulic system and an auxiliary hydraulic system connected to a single hydraulic pump. The process, generally, includes the steps of:

-   -   (1) obtaining an implement (pipelayer) fluid pressure         requirement from the implement (pipelayer) hydraulic system;     -   (2) obtaining an auxiliary implement fluid pressure requirement;     -   (3) determining a greatest system pressure requirement;     -   (4) transmitting the greatest system pressure requirement to the         single pump hydraulic system;     -   (5) obtaining fluid flow from the single pump hydraulic system         to maintain the greatest system pressure requirement; and     -   (6) maintaining fluid flow to satisfy the auxiliary implement         fluid pressure requirement independent of the implement         (pipelayer) system fluid pressure requirement.

Further aspects, features, and advantages of the present invention will be apparent to those of ordinary skill in the art upon examining the accompanying drawings and upon reading the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of a single pump parallel hydraulic system including the apparatus and process of the present disclosure.

FIG. 2 is a schematic diagram depicting the flow paths and electrical components of the manifold of the valve system of the present disclosure.

FIG. 3 is a top view of the manifold of the valve system of the present disclosure.

FIG. 4 is a front side view of the manifold of the valve system of the present disclosure.

FIG. 5 is a side view of the back side of the manifold of the valve system of the present disclosure.

FIG. 6 is a front end view of the manifold of the valve system of the present disclosure.

FIG. 7 is a back end view of the manifold of the valve system of the present disclosure.

FIG. 8 is a bottom view of the manifold of the valve system of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The system of the present disclosure in a preferred embodiment connects a pipelayer hydraulic system to a single-pump crawler tractor's implement valve in parallel. It gives precedence to the tractor's auxiliary hydraulic system by allowing the hydraulic power (pressure and flow) to be controlled to the hydraulic auxiliary system independently of the hydraulic pressure requirements of the implement hydraulic system. In this way, full control of the auxiliary device is maintained regardless of the implement hydraulic system's demands. A secondary function also allows either the auxiliary system or the implement system to dictate the pump's supply-pressure output. Without the system of the present disclosure installed, control of the auxiliary device and the implement would be unreliable with a hydraulic pipelayer system installed.

With reference to FIG. 1, a tractor hydraulic auxiliary system connected to a pipelayer hydraulic system in parallel 10 is disclosed. System 10 includes a tractor single-pump system 20, the load flow hydraulic fluid flow manifold of the present disclosure 30, auxiliary hydraulic system 40, tractor implement hydraulic system (such as a pipelayer) 50, and tractor hydraulic tank 60. In system 10, of the present disclosure load-flow manifold 30 and pipelayer system 50 are in a preferred embodiment connected to the implement valve of a crawler tractor in parallel such that the tractor single pump 20 is in fluid communication with load-flow manifold 30, which is, in turn, in fluid communication with both the auxiliary hydraulic system 40 and pipelayer hydraulic system 50. Single implement pump 20, auxiliary system implement 40, and pipelayer system 50 are in fluid communication with tractor hydraulic tank 60. The tractor auxiliary system may be any known system such as a counterweight used in combination with a pipelayer implement. Auxiliary counterweights of this kind may include a hydraulic activation system, such as 40, in the present disclosure, for manipulating the counterweight away from or toward the tractor in order to counter the weight of the pipelayer system.

Hydraulic fluid is pumped by tractor single implement pump 20 from hydraulic tank 60, shown by flow diagram 22. Hydraulic fluid is pumped by the tractor single pump 20 from hydraulic tank 20 into load flow manifold 30, as shown at 24. Load flow manifold 30 obtains the fluid flow pressure requirements of the tractor auxiliary system and provides hydraulic fluid flow required to auxiliary hydraulic system 40 necessary to actuate the auxiliary implement such as a counterweight as described above, as shown at 26. Load flow manifold 30 also obtains the fluid flow pressure requirements of implement (pipelayer) hydraulic system 50 and provides fluid flow to pipelayer hydraulic system 50 at 28. Load flow manifold 30 prioritizes the hydraulic fluid flow pressure requirements of auxiliary implement hydraulic system 40 regardless and independent of the fluid flow pressure demands of implement (pipelayer) hydraulic system 50. Fluid is returned by tractor auxiliary hydraulic system 40 to hydraulic tank 60, as shown at 32. Fluid is returned by pipelayer hydraulic system 50 to hydraulic tank 60, as shown at 34.

In a particular preferred embodiment, a crawler tractor with a single implement pump having a maximum flow of 56 gpm may be fitted with an implement system such as a hydraulic pipelayer draw works and an auxiliary implement system such as a hydraulic controlled counterweight. In such a system, the valve system 10 of the present disclosure including an auxiliary load flow manifold 30 may be implemented. In this preferred embodiment the manifold 30 includes a closed center valve typically employed with pipelayer counterweight controls in a load sensing system.

FIG. 2 is a flow and electrical schematic of the manifold 30 particularly suited in such an application. With reference to FIG. 2 taken in consideration with all the figures the operation of the valve of the present disclosure shall next be described.

In operation, the tractor auxiliary hydraulic system 40 provides a signal 42 to load flow manifold 30 regarding the fluid flow pressure required for proper auxiliary hydraulic system function. Pipelayer system 50 provides a signal 44 to load flow apparatus 30 regarding the fluid pressure requirement necessary for operation of the pipelayer system. From auxiliary hydraulic system pressure requirement signal 42 and pipelayer pressure requirement signal 44, load flow manifold 30 determines the greatest system pressure requirement 46 necessary for the proper function of auxiliary hydraulic system 40 and/or pipelayer hydraulic system 50. In a basic embodiment this is done by comparing the tractor auxiliary hydraulic system pressure requirement contained in signal 42 with the pipelayer hydraulic pressure requirement (contained in signal 44 to determine the larger-known as the greatest system pressure requirement. In this way, either the auxiliary hydraulic system or the implement hydraulic system may dictate the pump's supply-pressure output.

Load flow manifold 30 provides a signal 46 to single implement hydraulic pump 20 regarding this greatest system pressure requirement. Load flow manifold 30 may include a microprocessor for receiving signals 42 and 44 and for determining the greatest system pressure requirement and generating greatest system pressure requirement signal 46. This microprocessor may include as an output for providing the greatest system pressure requirement signal 46 to single pump system 20.

In a preferred embodiment the hydraulic fluid flow to the auxiliary hydraulic system 40 may be restricted in a predetermined manner such that it is less than the maximum hydraulic flow available from the single implement pump 20 since many common auxiliary hydraulic systems 40 do not require full pump flow. The remaining hydraulic fluid flow is available to the implement hydraulic system 50. Full hydraulic fluid flow is available to implement hydraulic system 50 when the auxiliary hydraulic system 40 is not in use.

In addition the valve system of the present disclosure 10 provides the ability to use a closed center valve—typically used with pipelayer counterweight controls—in a load sensing system. A closed center valve is preferred in the present system because an open center valve would always bleed off hydraulic flow to the auxiliary hydraulic system which could affect the required hydraulic flow to the implement hydraulic system and would additionally generate undesired heat which may cause wear to the components and other issues. In a closed center valve system as used in the present preferred embodiment, in a load sensing circuit, a bleed valve is inserted so as to slightly bleed the auxiliary load sense circuit which would prevent false load sense which otherwise may cause the system to malfunction. In a preferred arrangement, the bleed system would be much smaller than the restricted auxiliary flow system such that when the auxiliary system is in operation, auxiliary flow would not be affected.

In response to the greatest system pressure requirement contained in signal 46, the single implement hydraulic pump 20 provides the hydraulic fluid flow required to maintain the signaled greatest system pressure at 52. Load flow manifold 30 receives the hydraulic fluid flow required to maintain the greatest signaled system pressure 52 from implement hydraulic pump 20. Load flow manifold 30 prioritizes distribution of fluid flow to auxiliary hydraulic system 40 at the required pressure 54. Load flow manifold 30 then provides hydraulic fluid flow to pipelayer hydraulic system 50. In this way, load flow manifold 30 maintains at all times the required fluid flow to auxiliary hydraulic system 40 at the required fluid pressure, regardless and independent of the pipelayer hydraulic system 50. In the event that the pipelayer system pressure requirement (per signal 44) of pipelayer hydraulic system 50 is less than the auxiliary system requirement (per signal 42) of tractor steering system 40, load flow manifold 30 will provide the necessary fluid flow to auxiliary hydraulic system 40 required to maintain the auxiliary hydraulic system pressure requirement without a pressure drop due to fluid flow taking the path of least resistance caused by the lower pressure request of pipelayer hydraulic system 50. However, tractor auxiliary hydraulic systems commonly do not require high flow and pressure to operate. In this regard it may be disadvantageous to supply the maximum pressure available to the auxiliary hydraulic system since it may cause it to operate quicker than designed/desired/required and this makes it more difficult to control.

When the hydraulic fluid flow enters the manifold 30 at 70, a modulator valve 72 signals the flow and pressure required for the respective systems. The modulator valve 72 further reduces the greatest pressure from the implement pump 20 to the required pressure of either the auxiliary hydraulic system 40 or the pipelayer hydraulic system 50 (whichever is lower). The flow pressure required by the pipelayer hydraulic system 50 is supplied from manifold 30 through a pipelayer valve 74. The fluid pressure required by the auxiliary hydraulic system 40 is supplied through an auxiliary flow valve 76. However, since the auxiliary hydraulic system 40 does not commonly require full pump flow resulting from the priority afforded it, the hydraulic flow to the auxiliary hydraulic system may be mechanically restricted at 78. For example, in the preferred arrangement described herein, the flow to the hydraulic system may be restricted to eight gallons per minute (8 gpm). Accordingly, a system including an implement pump 20 capable of a maximum flow of 56 gpm giving priority to an auxiliary hydraulic system of 8 gpm leaves 48 gpm available for the pipelayer hydraulic system 50 through pipelayer valve 74. In this embodiment, 48 gpm will always be available to the pipelayer hydraulic system which is capable of full operation at all times. It is understood, however, that different embodiments could be constructed using different maximum and restricted flow requirements such that the flow to pipelayer hydraulic system 50 may be reduced to slow its operation in certain embodiments.

In a closed center system employing a load sensing circuit 80, in fluid communication with modulator 72, includes a pump load sense valve 82, a pipelayer load sense valve 84, an auxiliary load sense valve 86 and a bleed load sense valve 88. The auxiliary hydraulic system 40 in the preferred embodiment will include a bleed valve 88 which includes a bleed restriction 90. Bleed restriction 90 is a mechanical restriction of a desired structure. In the preferred embodiment described herein, the bleed restriction would allow 0.1 gpm to bleed from the auxiliary flow system. In that the bleed of 0.1 gpm is much less than the restricted flow of the auxiliary hydraulic system 40 of 8 gpm, when the auxiliary hydraulic system 40 is in operation, the bleed is small enough so as not to affect the function of the auxiliary hydraulic system 40.

Load flow apparatus 30 may provide the necessary fluid flow to maintain the required system pressure in either auxiliary hydraulic system 40 or pipelayer hydraulic system 50, depending on which signals the greatest system pressure requirement, which then becomes the greatest system pressure requirement contained in signal 46. In this way, either the tractor steering system 40 or the pipelayer system 50 may dictate the pump flow 52 required to maintain the greatest system pressure (contained in signal 46). Pump 20 is then actuated to provide the greatest system pressure 52 into load flow manifold as shown at 24. Load flow manifold 30 then supplies the respective requisite flow and pressure to the auxiliary hydraulic system and/or the implement (pipelayer) system. When the auxiliary hydraulic system is not in use, full flow is available to the implement hydraulic system.

Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims. 

What is claimed is:
 1. A process for managing fluid flow requirements for a tractor auxiliary hydraulic system and an implement hydraulic system connected in parallel to a single pump hydraulic system, comprising: obtaining an implement (pipelayer) fluid pressure requirement from the implement (pipelayer) hydraulic system; obtaining an auxiliary implement fluid pressure requirement; determining a greatest system pressure requirement; transmitting the greatest system pressure requirement to the single pump hydraulic system; obtaining fluid flow from the single pump hydraulic system to maintain the greatest system pressure requirement; and maintaining fluid flow to satisfy the auxiliary implement fluid pressure requirement independent of the implement (pipelayer) system fluid pressure requirement.
 2. The process of claim 1 further restricting the auxiliary fluid flow to the auxiliary hydraulic system to a predetermined valve.
 3. The process of claim 2 wherein the single pump hydraulic system includes a maximum pump capacity and wherein said predetermined valve is less than said maximum pump capacity.
 4. The process of claim 3 wherein the maximum pump capacity minus the predetermined valve of the restricted fluid flow to the auxiliary hydraulic system is greater than or equal to the fluid pressure requirement of the implement hydraulic system.
 5. The process of claim 1 wherein fluid flow is provided to the implement hydraulic system necessary to satisfy the implement hydraulic system fluid pressure requirement.
 6. The process of claim 5 wherein when the auxiliary hydraulic system is not in use the greatest system pressure requirement will be equal to the implement fluid pressure requirement.
 7. The process of claim 1 wherein fluid flow is bled from the auxiliary hydraulic system.
 8. The process of claim 2 wherein fluid flow is bled from the auxiliary hydraulic system.
 9. The process of claim 8 wherein the fluid flow bled from the auxiliary hydraulic system is less than said predetermined valve.
 11. A process for managing fluid flow requirements for an auxiliary implement hydraulic system and an implement hydraulic system connected in parallel to a single pump hydraulic system, comprising: obtaining an implement fluid pressure requirement from the implement hydraulic system; obtaining an auxiliary implement fluid pressure requirement from the auxiliary implement hydraulic system; determining a greatest system pressure requirement; transmitting said greatest system pressure requirement to the single hydraulic pump; obtaining fluid flow from said single hydraulic pump to maintain said greatest system pressure requirement; maintaining an essential operation fluid flow to satisfy said essential operation fluid pressure requirement independent of said implement fluid pressure requirement; and restricting the auxiliary fluid flow to the auxiliary hydraulic system to a predetermined valve.
 11. The process of claim 10 wherein the single pump hydraulic system includes a maximum pump capacity and wherein said predetermined valve is less than said maximum pump capacity.
 12. The process of claim 11 wherein the maximum pump capacity minus the predetermined valve of the restricted fluid flow to the auxiliary hydraulic system is greater than or equal to the fluid pressure requirement of the implement hydraulic system.
 13. The process of claim 10 wherein fluid flow is provided to the implement hydraulic system necessary to satisfy the implement hydraulic system fluid pressure requirement.
 14. The process of claim 10 wherein fluid flow is bled from the auxiliary hydraulic system.
 15. The process of claim 14 wherein the fluid flow bled from the auxiliary hydraulic system is less than said predetermined valve. 